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75 Cards in this Set
- Front
- Back
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Spontaneous mutations |
Natural and random, caused by procesdes within cell |
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Induced mutations |
Extraneous factor, natural or artificial |
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Somatic mutations |
Any cell except germ cells, not heritable |
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Germ-line mutations |
Found in gametes and are inherited |
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Types of mutations based on phenotype |
Loss of function (null) Hypomorphic Hypermorphic Neutral mutation Gain of function Nutritional (biochemical) Regulatory Condituonal mutations |
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Types of conditional mutations |
Temperature Chemical |
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Loss of function (null) |
No gene product |
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Hypomorphic |
Lower level of gene expression |
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Hypermorphic |
Higher level of gene expression |
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Neutral mutation |
No effect on gene expression or product of gene |
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Gain of function |
Gene product works differently |
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Nutritional (biochemical) |
Inability to synthesize required nutrients, like leucine or tryptophan |
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Regulatory |
Gene promoter is affected |
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Conditional mutations |
Gene can be turned on and off at discretion of researcher |
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Temperature |
Temp affects gene expression |
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Chemical |
An added chemical affects gene expression |
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Point mutations |
Base substitutions in which one base pair is altered |
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Classifications of point mutations |
Transition Transversion |
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Transition |
Pyr replaces a pyr, or pur replaces pur |
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Transversion |
Pur and pyr are interchanged |
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Types of point mutations |
Missense Nonsense Silent Neutral |
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Causes of spontaneous mutations |
Replicatuon errors and slippage Tautomeric shift Depurination Deamination Oxidative damage |
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Replication errors and slippage |
Incorrect base incorporated and slippage usually in areas of repeated sequence |
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Tautomeric shift |
Bases can take several forms, allowing different h bonds |
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Depurination |
Loss of nitrogenous base, usually A or G, creates apurinic site (AP) |
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Deamination |
Conversion of amino to keto group |
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Oxidative damage |
Damages dna, radicals produced in metabolism |
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Kinds of induced mutations |
Base analogs Alkylating agents Acridine dyes Uv light Ionizing radiation |
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Base analogs |
5 bromouracil, in enol form can bind to G instead of A |
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Alkylating agents |
Ems, mustard gases |
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Acridine dyes |
Intercalates, interferes with replication, frameshifts |
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UV light |
Pyrimidine dimers |
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Ionizing radiation |
Free radicals |
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Trinucleotide repeats |
An increase in number of a repeated sequence to a certain number that can disrupt function of a gene |
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Chiasmata |
Regions of crossing over |
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Interference |
Reduces expected number of multiple crossovers + = fewer crossovers than expected - = more crossovers than expected |
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Operons |
Group of genes regulated together |
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Constitutive |
Always on regardless of environment |
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Inducible |
Usually off but turned on under certain conditions |
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Repressible |
Usually on, turned off under certain conditions |
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Negative control |
Regulatory molecule shuts down |
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Positive control |
Regulatory molecule turns on |
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Polycistronic |
One mRNA that can make multiple proteins |
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Lac operon |
Repressor gene-I Promoter- P Operator - O Structural genes- Z,A,Y Inducible |
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LacI- |
Repressor mutated, cant bind to operator |
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LacOc |
Operatie region mutated, repressor cant bind |
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Constitutively active mutants |
Always turned on LacI- LacOc |
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Constitutively repressed mutant |
Always turned off LacIs |
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LacIs |
Repressor mutated so lactose cant bind |
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Merozygote |
Partial diploid |
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Dominance levels of mutants |
Oc > Is > I+ > I- |
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CAP |
Catabolite activating protein |
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AC |
Adenyl cyclase |
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No glucose, with lactose |
CAP and cAMP can bind Those bind to promoter Allows transcription |
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No glucose, no lactose |
No transcription |
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With glucose |
AC inhibited cAMP can't form CAP can't bind to promoter No transcription |
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Tryptophan operon |
Promoter, operator, leader, attenuator Repressible system |
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trpR- mutant |
Constitutively on No trp= high expression Trp=low levels of expression |
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Attenuation |
Secondary mechanisn that regulates how much expression occurs based on presence of tryptophan |
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With enough tryp |
Hairpin with 3 and 4 Terminates transcription |
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Not enough tryp |
Translation stalls Hairpin btwn 2 and 3 Transcription continues |
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Points of regulation |
Transcription Processing Transport Degradation Translation Protein modification Chromatin remodeling Dna methylation |
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Chromatin remodeling |
Histone acetylation- reduces affinity of histone for dna |
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Dna methylation |
Adding methyl group to cytosine Activates and deactivates genes |
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Transcription regulation |
Promoters Enhancers and silencers Transcription factors |
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Promoters |
Basal level |
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Enhancers |
Full level |
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Silencers |
Reduced levels |
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Transcription factors |
Proteins that modify gene expression |
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2 domains of transcription factors |
Dna binding domain Transactivating (or repression) domain: activates transcription |
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Basal transcription factors |
Interact with RNA pol II |
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Activator transcription factors |
Interact with enhancer region Gene specific |
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RNAi (RNA interference) |
Prevents mRNAs from being translated by degrading it or preventing translation Initiated by double stranded RNA Goal is to down regulate gene expression |
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Small interfering RNA (siRNA) and process |
Delivered from outside Double stranded Dicer recognizes and cuts into 21 nt fragments Fragments go to RISC RISC finds homologous sequence in mRNA ans degrades it Long term inhibition |
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Micro RNA (miRNA) and process |
Endogenous (comes from inside) Single stranded that forms hairpin loop Dicer recognizes loop and cuts Silences transcription Regulate developmental genes |
